The present invention concerns a metallized polyester film capacitor. More in particular, the present invention relates to a metallized polyester film capacitor having excellent moist heat resistance made by the use of a film having an improved adhesion between a substrate film and a vapor-deposited metal.
Since polyester films are excellent, for example, in mechanical property, heat resistance and electric property, they are generally used as elements fabricated by winding two polyester films which are vapor-deposited with a metal such as Al or Zn, or fabricated by laminating a plurality of such films and then cut into chips. With the progress in various kinds of electric devices and equipments in recent years, improvement for the characteristics of the polyester film capacitors has been intended. One of the requirements for the improvement of the characteristics is moisture resistance and heat stability for a long period of time. That is, the metallized polyester film has a drawback that the adhesion between the substrate film and the vapor-deposited metal, in particular, the adhesion under high temperature and high humidity atmosphere is poor to bring about a problem that if a capacitor is put under a high temperature and high humidity condition, moisture permeates through the interface between the substrate film and the vapor-deposited metal thereby changing the static capacitance of the capacitor with elapse of time. Accordingly, improvement has been demanded for moist heat resistance of the capacitor from a viewpoint of a long term stability.
There have been disclosed a film capacitor having a vinylidene chloride coating layer in Japanese Patent Application Laid-Open (KOKAI) No. 60-115214 and a film capacitor having a coating layer containing melamine and/or urea resin as the essential ingredient in Japanese Patent Application Laid-Open (KOKAI) No. 60-120511, respectively, as the capacitor of excellent moist heat resistance.
However, even if the resin composition as disclosed in the above-mentioned publications is used, the performance of the capacitor can not be maintained sufficiently in a moist and high temperature circumstance. Further, along with remarkable development for various kinds of electronic equipments in recent years, demand for the long term reliability required for a capacitor, in particular, the long term moisture and heat stability of a capacitor performance has been increased further.